The present application is related to application number JP(A) 11-114782, filed in Japan, the entire contents of which are hereby incorporated by reference.
The present invention relates to an image reading device capable of selecting a first reading method for reading a document by moving the document while the reading means is stationary, a second reading method for reading a document by moving the reading means while the document is stationary, an image reading method, a computer program product for storing an image reading sequence, and an image forming apparatus.
Conventionally, the reading methods used in image reading devices include a sheet-through scanning method for reading a document while the document moves relative to a stationary reading unit, and a flatbed scanning method for reading a document while the reading unit moves relative to the stationary document.
The sheet-through scanning method is suitable for high-speed reading because the documents are sequentially fed at high-speed to a reading unit, but are unsuitable for reading color documents due to the difficulty of achieving high-precision document transport control due to differences in thickness and friction coefficient corresponding to the type of document. The flatbed scanning method is appropriate for reading color documents due to the ease of achieving high-precision control of the movement of the reading unit, but is inappropriate for high-speed reading because the reading unit must be moved and has considerable weight.
Conventional art utilizing the mutual advantages of the two methods include, for example, Japanese-Laid-Open Patent Application No. HEI 9-261417, which discloses a reading device which performs a preliminary scan of a plurality of documents via a sheet-through method, and after determining whether each document is a color document or a monochrome document, scans the color documents via the flatbed scan method, and scans the monochrome documents via the sheet-through method. Japanese Laid-Open Patent Application No. HEI 7-273952 discloses a reading device which determines whether or not a document is a color document before reading the document, and reduces the document transport speed for color documents so as to improve the reading accuracy of color documents by the sheet-through scan method.
In the art of the former disclosure, however, a disadvantage arises in that extra time is required to conduct a preliminary scan of all the documents to determine whether the document is a color document or a monochrome document. Moreover, in the art of the latter disclosure, it is difficult to read a document via the sheet-through method at greater accuracy than the flatbed scan method even when the document transport speed is reduced due to differences in friction coefficient and document type, thereby leading to the possibility of color shift in the case of color documents.
A first object of the present invention is to provide an image reading device and an image reading method for utilizing the respective advantages of the sheet-through and flatbed scan methods which reduce the entire reading time when reading a mixture of color and monochrome documents. A second object of the present invention is to provide an image reading device and an image reading method which do not produce color-shifts in color documents. A third object of the present invention is to provide a computer program product for storing image reading instructions. Another object of the present invention is to provide an image forming apparatus that utilizes this image reading device.
These objects of the present invention-are attained by the means described below.
In a first aspect of the present invention, an image reading device includes a reader for reading a document thereby obtaining image data. The position of the reader can be moved relative to the document being read. The image reading device further includes a controller that operates the reader in one of two modes. The first reading mode moves the document relative to the reader while the reader is stationary. The second mode moves the reader relative to the document while the document is stationary. After the document is read in the first mode, a decision unit determines whether the obtained image data correspond to color image data or monochrome image data. An output controller then outputs the image data if the image data is monochrome image data. If the image data is color image data, the document is read by the second mode, and the second mode image data is output.
In a second aspect of the present invention, an image reading method is disclosed. This method includes reading a document by moving a document relative to a stationary reader to obtain image data. The resultant image data is then determined to represent either monochrome image data or color image data. If the image data represent monochrome image data, the image data is outputted. However, if the image data represent color image data, the document is read a second time by moving the reader relative to a stationary document to obtain image data. The image data from the second reading is then output.
In a third aspect of the present invention, a computer program product is disclosed. This product includes instructions for recording image data. The instructions include first instructions to read a document that moves relative to a reader that is stationary in order to obtain image data. The second instructions are to determine whether the image data obtained by the first instruction represent a color image or a monochrome image. If the second instructions determine the image data represent monochrome data, the third instructions are executed which output the image data from the first instructions, and no more instructions are executed. If the second instructions determine the image data represent color image data, the fourth instructions are executed. The fourth instructions are to read the document that is stationary by a reader that moves relative to the document in order to obtain image data. The fifth instructions are to output the image data from the fourth instructions.